Pneumatically operated nailing machine

ABSTRACT

A pneumatically operated nailing machine includes a reciprocatable blade for driving nails when advanced and a reciprocatable differential piston unit connected to the blade advances and retracts the blade. A cylinder member reciprocatingly receives the upper small diameter piston of the differential piston unit and a reciprocatable cylinder sleeve reciprocatingly receives the lower large diameter piston thereof. Sealing means seals the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston. Valving means for the differential piston unit include an annular upwardly facing valve seat on the cylinder sleeve, a stationary annular upwardly facing valve seat adjacent the valve seat on the cylinder sleeve, and a valve sleeve having a downwardly facing annular valve ring adapted to engage said valve seats. Means including passageways supply air under pressure beneath the upper small diameter piston and vent to atmosphere air above the lower large diameter piston to drive the differential piston unit upwardly and retract the blade when the cylinder sleeve is moved upwardly to engage its annular valve seat with the annular valve ring and to disengage the annular valve ring from the stationary annular valve seat. Said means including passageways interrupt the venting of air to atmosphere from above the large diameter piston and supply air under pressure above the large diameter piston to drive the differential piston unit downwardly and advance the blade when the cylinder sleeve is moved downwardly to engage the annular valve ring with the stationary annular valve seat and to disengage its annular valve seat from the annular valve ring. Means including control valve means selectively move the cylinder sleeve and valve sleeve upwardly and downwardly.

United States Patent lnventor Edgar P. Anstett 2i Lakewood Place, Highland Park, II]. 60035 Appl. No. 5,195

Filed Jan. 23, 1970 Patented Aug. 24, 197] PNEUMATICALLY OPERATED NAIUNG MACHINE Primary Examiner--Granville Y. Custer, Jr. Attorney-Wallenstein, Spangenberg, Hattis & Strampel ABSTRACT: A pneumatically operated nailing machine includes a reciprocatable blade for driving nails when advanced and a reciprocatable differential piston unit connected to the blade advances and retracts the blade. A cylinder member reciprocatingly receives the upper small diameter piston of the differential piston unit and a reciprocatable cylinder sleeve reciprocatingly receives the lower large diameter piston thereof. Sealing means seals the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston. Valving means for the differential piston unit include an annular upwardly facing valve seat on the cylinder sleeve, a stationary annular upwardly facing valve seat adjacent the valve seat on the cylinder sleeve, and a valve sleeve having a downwardly facing annular valve ring adapted to engage said valve seats. Means including passageways supply air under pressure beneath the upper small diameter piston and vent to atmosphere air above the lower large diameter piston to drive the differential piston unit upwardly and retract the blade when the cylinder sleeve is moved upwardly to engage its annular valve seat with the annular valve ring and to disengage the annular valve ring from the stationary annular valve seat. Said means including passageways interrupt the venting of air to atmosphere from above the large diameter piston and supply air under pressure above the large diameter piston to drive the differential piston unit downwardly and advance the blade when the cylinder sleeve is moved downwardly to engage the annular valve ring with the stationary annular valve seat and to disengage its annular valve seat from the annular valve ring. Means including control valve means selectively move the cylinder sleeve and valve sleeve upwardly and downwardly.

PATENTED AU824 |97| SHEET 1 BF 5 PNEUMATICALLY OPERATED NAILING MACK-[ENE The principal object of this invention is to provide an improved pneumatically operated nailing machine which is simple in construction and rugged and foolproof in operation, which may be inexpensively manufactured and assembled, which is economical in operation, which utilizes a minimum amount of compressed air but provides maximum nailing force, and which eliminates unwanted escape of air by reason of its valving action.

Briefly, in accordance with the preferred embodiment of this invention, the pneumatically operated nailing machine includes a hollow housing which is supplied with air under pressure, a reciprocatable blade which extends through the bottom of the housing for driving nails when advanced, a reciprocatable differential piston unit which is located in the housing and which has a lower large diameter piston and an upper small diameter piston connected by a piston rod, and means which secures the blade to the lower end of the differential piston unit so as to advance and retract the blade as the differential piston unit is reciprocated. A cylinder sleeve is reciprocatably mounted in the housing and it has a cylinder portion reciprocatingly receiving the lower large diameter piston of the differential piston unit. This cylinder sleeve has at its upper end an upwardly facing annular valve seat and an annular piston shoulder of small area therearound subject to the air under pressure in the housing and it also has intermediate its ends an annular piston flange of large area therearound. A cylinder member is located in the housing and it has a cylinder reciprocatingly receiving the upper small diameter piston of the differential piston unit.

The cylinder member also has sealing means for the piston rod of the differential piston unit for sealing the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston and it further has an upwardly facing annular valve seat of smaller diameter than the annular valve seat at the upper end of the cylinder sleeve and located adjacent thereto and radially spaced inwardly therefrom. A valve sleeve is reciprocatingly carried by the cylinder member and it has a downwardly facing annular valve ring engageable with the upwardly facing annular valve seats of the cylinder sleeve and the cylinder member and also has an annular piston shoulder subject to the air under pressure in the housing. The cylinder member includes passageways for venting to at mosphere the upwardly facing annular valve seat thereof and the cylinder thereof above the upper small diameter piston of the differential piston unit. The housing has passageways for venting to atmosphere the cylinder of the cylinder sleeve below the lower large diameter piston of the differential piston unit. The cylinder member also has passageways for continuously supplying air under pressure from the hollow housing to the cylinder thereof below the upper small diameter piston of the differential piston unit.

Means including control valve means, when in one condition, supply air under pressure from the housing below the annular piston flange of the cylinder sleeve for moving the same upwardly to cause the annular valve seat thereof to engage the annular valve ring of the valve sleeve and to move the valve sleeve upwardly to disengage the annular valve ring thereof from the annular valve seat of the cylinder member for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the air under pressure in the housing and for venting the same to atmosphere. As a result, the air under pressure in the cylinder of the cylinder member below the upper small diameter piston of the differential piston unit moves the same upwardly to retract the nail-driving blade.

The aforementioned means including said control valve means is also operative, when in another condition, for venting to atmosphere air from below the annular piston flange of the cylinder sleeve for allowing the air under pressure in the housing acting on the annular piston shoulder of the valve sleeve and the annular piston shoulder of the cylinder sleeve to move the same downwardly. This causes the annular valve ring ofthe valve sleeve to engage the annular valve seat of the cylinder member and to disengage the annular valve seat of the cylinder sleeve from the annular valve ring of the valve sleeve for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the atmosphere and for supplying air under pressure thereto from the housing. As a result, the air under pressure in the cylinder ofthe cylinder sleeve above the large diameter piston of the differential piston unit overcomes the force of the air under pressure in the cylinder member below the small diameter piston of the differential piston unit and moves the same downwardly to advance the nail-driving blade.

The aforesaid control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed, and a second valve having a normal position and movable to a second position when a control trigger is manually depressed. The arrangement is such that air from below the piston flange of the cylinder sleeve is vented to atmosphere to move the cylinder sleeve downwardly and advance the nail-driving blade only when both valves are moved to their second positions. These first and second valves are located in bores in a valve housing arranged in the machine housing and the bores and passages associated with the valves are sealed against leakage.

The hollow housing has an upper portion of large transverse dimensions which is supplied with the air under pressure, a lower cylindrical portion of small transverse dimension which slidable mounts the lower part of the cylinder sleeve, and an intermediate portion of intermediate transverse dimension which forms a cylinder for receiving the annular piston flange of the cylinder sleeve. This annular piston flange has packing for slidably sealing the same to the intermediate portion of the housing. The housing carries upper and lower packings slidably receiving the cylinder sleeve for sealing the upper portion of the housing from the cylinder forming intermediate portion of the housing and for sealing the cylinder forming intermediate portion of the housing from the lower portion of the housing. The upper small diameter piston and the lower large diameter piston of the differential piston unit have packing for slidably sealing the same in the cylinder of the cylinder member and in the cylinder of the cylinder sleeve. These packings are preferably V-type packings.

The housing includes a foot plate secured thereto below the cylinder sleeve and the lower large diameter piston of the differential piston unit through which the reciprocatable blade extends. An annular rubber bumper is carried by the foot plate around the reciprocatable blade to be engaged by the lower large diameter piston of the differential piston unit when the latter is moved downwardly. The foot plate is provided with vent passages about the annular rubber bumper for directing the air, which is vented to atmosphere from below the differential piston unit when the latter is reciprocated, about the annular rubber bumper for cooling the same. A nail guide plate is carried by the foot plate for guiding the reciprocatable blade and a nail to be driven thereby, and a magazine is carried by the foot plate for feeding nails to the nail guide plate.

The upper end of the reciprocatable nail-driving blade is T- shaped, and the means for securing the blade to the lower end of the differential piston unit includes a two-part separable holder secured to the lower end of the differential piston unit and encompassing the upper end of the blade. The holder has shoulders engageable by the undersides of the T-shaped portion of said blade, and a backup plate within the holder is engageable b the top side of the T-shaped portion of the blade when the differential piston unit advances the blade for driving nails.

Further objects of this invention reside in the details of construction of the pneumatically operated nailing machine and in the cooperative relationships between the component parts thereof.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings in which:

FIG. 1 is a side elevational view of a preferred form of the pneumatically operated nailing machine of this invention;

FIG. 2 is a partial front elevational view of the nailing machine looking from the left of FIG. 1;

FIG. 3 is a rear elevational view ofthe nailing machine looking from the right of FIG. 1;

FIG. 4 is an enlarged vertical sectional view through the nailing machine taken substantially along the line 4-4 of FIG. 3 and showing the differential piston unit in its upper position;

FIG. 5 is an enlarged sectional view of the upper portion of FIG. 4 illustrating the upper small diameter piston of the differential piston unit;

FIG. 6 is a horizontal sectional view through the two part holder for the nail driving blade taken substantially along the line 6-6 of FIG. 4;

FIG. 7 is an elevational view of one of the parts of the blade holder of FIG. 6 and taken substantially along the line 7-7 of FIG. 6;

FIG. 8 is an exploded perspective view of the nail driving blade and its holder by which it is secured to the differential piston unit;

FIG. 9 is a vertical sectional view similar to FIG. 4 and taken substantially along the line 4-4 of FIG. 3 but illustrating the differential piston unit in its down position;

FIG. 10 is a horizontal sectional view of the stationary valve disc and taken substantially along the line 10-10 of FIG. 9;

FIG. 11 is an enlarged and exploded partial sectional view of the valve sleeve and its valve ring showing the manner of securing the valve ring to the valve sleeve;

FIG. 12 is a sectional view similar to FIG. 11 but showing the valve ring secured in place on the valve sleeve;

FIG. 13 is a side elevational view of the two part cylinder member utilized in the nailing machine;

FIG. 14 is a horizontal sectional view through the two part cylinder member taken substantially along the line 14-14 of FIG. 13;

FIG. 15 is a bottom view of the two part cylinder member looking from the bottom of FIG. 13;

FIG. 16 is a partial side elevational view of the inner part of the two part cylinder member;

FIG. 17 is a horizontal sectional view through the nailing machine taken substantially along the line 17-17 of FIG. 4;

FIG. 18 is a vertical sectional view through the nailing machine taken substantially along the line 18-18 of FIGS. 4 and 17;

FIG. 19 is an enlarged sectional view through the control valve means illustrating the valves thereof in their normal positions; and

FIG. 20 is a sectional view similar to FIG. 19 but showing the valves thereofin their second positions.

Referring first to FIGS. 1 to 4 and 9, a preferred form ofthe pneumatically operated nailing machine of this invention is generally designated at 10. It includes a hollow housing 11 having a handle portion 12 provided with a cavity 13 to which air under pressure is supplied by a fitting 14. The upper portion of the motor part of the hollow housing 11 has a cavity 15 of large transverse dimensions which communicates with the cavity 13 of the handle portion 12 for being supplied with air under pressure. The hollow housing 11 also has an intermediate cavity portion 16 of intermediate transverse dimension which forms a cylinder portion for the piston flange of the cylinder sleeve. The hollow housing 11 also has a lower internal cylindrical portion 17 of small transverse dimension which slidably mounts the lower part of the cylinder sleeve. The hollow housing 11 may be formed of any suitable material, such as, die cast aluminum, or the like.

A cylinder sleeve 20 is reciprocatably received in the hollow housing 11 and has its lower portion slidably mounted in the lower cylindrical portion 17 of the hollow housing 11. The cylinder sleeve 20 is provided with an internal cylinder 21 for the reciprocatable differential piston unit. At its upper end the cylinder sleeve 20 is provided with an upwardly facing annular valve seat 23 and an annular piston shoulder 22 of small area therearound, this annular piston shoulder 22 being subject to the air under pressure in the hollow housing 11. Intermediate its ends the cylinder sleeve 20 is provided with an annular piston flange 30 which in turn is provided with a packing 31. The cylinder sleeve 20 may be formed of any suitable material and, preferably, it is molded from a suitable rigid synthetic plastic material. The packing 31 is preferably a cup-shaped packing which is preferably formed from a suitable resilient synthetic rubber or rubberlike plastic material, such as, buna rubbers, particularly buna N rubber, or the like, it being held in place in a groove in the cylinder sleeve 20 and being backed by the annular piston flange 30. The annular piston flange 30 and its packing 31 operate in the intermediate cylinder portion 16 of the hollow housing 11, the packing 31 forming an airtight seal.

The upper portion 15 of the hollow housing 11 is sealed from the intermediate portion 16 thereof by sealing means which include a seal 24 secured to a backing ring 25. The seal 24 is preferably V-shaped and may be formed of a suitable resilient synthetic rubber of rubber like plastic material which is molded to the backing ring 25. The seal 24, 25 rests against a shoulder in the hollow housing 11 and, in addition to friction, it is also held in place by the air pressure in the hollow housing 11. Thus, the upper side of the piston flange 30 is not affected by air under pressure in the upper portion 15 of the hollow housing 11. The bottom of the intermediate portion 16 of the hollow housing 11 is sealed by packing 26 which preferably is a V-shaped packing which is received in a suitable groove in the housing. This Vshapcd packing 26 is preferably formed from a suitable resilient synthetic rubber or rubberlike plastic material. The bottom ofthe cylinder sleeve 20 is also provided with an O ring 27 for further sealing the cylinder sleeve 20 with respect to the lower portion 17 of the hollow housing 11. A lubricant fitting 28 is provided in the hollow housing between the sealing means 24 and the piston flange 30 for lubricating the intermediate cylinder portion 16 receiving the piston flange 30. Likewise, a lubricant fitting 29 is carried by the housing 11 between the sealing means 26 and the O ring 27 for lubricating the lower small diameter portion 17 of the hollow housing 11. It will be noted that these lubricating fittings 28 and 29 are not subject to air under pressure. These fittings 28 and 29 and/or vent openings (not shown) vent to atmosphere the spaces between the sealing means 24 and the piston flange 30 and between the sealing means 26 and the O ring 27.

As shown more clearly in FIGS. 4, 9 and 13 to 16, the nailing machine also includes a two-part cylinder member, the inner part having a bottom portion 32 and a top portion 33 which is provided with an internal cylinder 34. The bottom portion 32 is provided with an internal shoulder 35 and is also circumferentially provided with a plurality of half-round slots 36 which communicate with an upper annular shoulder 37. The outer part 39 of the cylinder member has a plurality of circumferentially arranged half-round slots 40 on the inside thereof, these slots 40 communicating at their bottoms with radially extending notches 41. When the inner and outer parts of the cylinder member are assembled together, the circumferentially spaced slots 36 and 40 therein form vertically extending circular passages communicating the slots 41 at the bottom of the outer part 39 with the annular shoulder 37 on the inner part 32. Near its upper end the outer part 39 of the cylinder member is provided with an annular groove 42 and this annular groove 42 is communicated to the inside cylinder 34 of the cylinder part 33 by aligned passages 43 and 44, the passage 43 being in the part 39 and the passage 44 being in the part 32. The juncture between the inner and outer parts 32 and 39 about the passages 43 and 44 is sealed by an O ring 45. The parts 32, 33 and 39 may be made of any suitable material but, preferably, they are molded from a suitable rigid synthetic plastic material.

Engaging the bottom of the inner and outer parts of the cylinder member 32, 39 is a valve disc 47 having an upwardly facing annular valve seat 48, the valve seat 48 being adjacent to and radially inwardly from the upwardly facing annular valve seat 23 of the cylinder sleeve 20. Screws 49 extending through suitable holes in the valve disc 47 and through certain of the passages 36, 40 in the cylinder member are threaded into a cover 50 for securing the valve disc 47 and the two-part cylinder member 32, 39 to the cover 50. The cover 50 is pro vided with a hole 51 which communicates with the shoulder 37, the passages 36, 40 and the slots 41 of the cylinder member above the upwardly facing annular valve seat 48 of the valve disc 47. In this way, the upwardly facing annular valve seat 48 is vented to atmosphere. The upper end of the outer portion 39 of the cylinder member is provided with a seal ring 52 for sealing the same against the cover 50. The radial passage 43, 44 operates to supply air under pressure from the hollow housing 11 to the cylinder 34 in the cylinder member. The cover 50 is secured to the hollow housing 11 by means of screws 53 and an O ring 54 forms a seal between the hollow housing 11 and the cover 50. The cover 50 may be formed of any suitable material, such as, die cast aluminum, or

the like, and the valve disc 47 may be formed from a suitable metal, such as, steel, or the like.

A valve sleeve 56 is reciprocatingly mounted on the outer portion 39 of the cylinder member and O-rings 57 form seals therebetween. The valve sleeve 56 is provided with an annular piston shoulder 58 which is subject to the air under pressure in the hollow housing 11. The valve sleeve 56 may be formed of any suitable material but preferably it is molded from a suitable rigid synthetic plastic material. The valve sleeve 56 is provided with an annular slot 59 which receives a downwardly facing valve ring 60. The valve ring 60 is preferably formed from a suitable resilient synthetic rubber or rubberlike plastic material and, as shown more clearly in FIG. 11, it has annular ribs 61 therearound. A vent passage 62 communicates with the annular groove 59 so that when the valve ring 60 is forced into the annular groove 59, air trapped in the annular groove 59 will be vented to atmosphere. Thus, the valve ring 60 may be completely inserted in the annular groove 59 without the trapping of any air. After the valve ring 60 is so inserted in the annular groove 59, a plug 63 is inserted in the vent passage 62 so as to close the same, as shown in FIG. 12. As a result, the valve ring 60 in addition to being held in place in the annular groove 59 by friction it is also held in place by vacuum. The upper end of the valve sleeve 56 is provided with slots 64 which operate to throttle the supply of air to the cylinder 34 as the valve sleeve 56 is raised from the position shown in FIG. 9 to the position shown in FIG. 4.

The differential piston unit designated at 67 has a lower large diameter piston 68 arranged within the cylinder 21 of the cylinder sleeve and an upper small diameter piston 69 arranged in the cylinder 34 of the cylinder member 33 and a piston rod 70 connecting the pistons 68 and 69 together. The small diameter piston 69 is provided with a packing 71 which is held in place by a washer 72 when a screw 73 secures the piston 69 to the piston rod 70. The piston rod 70 is in the form of a tube and is provided with screw threads at its upper end for receiving the screw 73. The packing 71 is preferably a V- shaped packing made of a suitable resilient synthetic rubber or rubberlike plastic material and it operates to form a seal between the piston 69 and the cylinder 34. The piston 69 may be formed of any suitable material and preferably it is molded from a suitable rigid synthetic plastic material.

The lower large diameter piston 68 is preferably formed from metal, such as, steel, or the like, and it is provided with a packing 75 which is preferably cup-shaped and which is preferably molded from a suitable resilient synthetic rubber or rubberlike plastic material. The packing 75 is snapped into a groove in the piston 68 for holding the same in place on the piston 68. The bottom of the piston 68 is provided with an annular shoulder 76 which receives and captures a two part holder 77, the details of which are shown more clearly in FIGS. 6 to 8. The holder is provided with a central cavity having internal flats 78 for receiving the head 79 of a screw 81, the head 79 having flats 80 mating with the flats 78 in the holder 77. The screw 81 extends through a hole in the piston 68 and screw threadedly receives a nut 82 for securing the holder 77, piston 68 and screw 81 together. The screw 81 also has a reduced threaded portion 83 which is threaded into the piston rod 70 for securing the piston 68 to the piston rod 70. The two-part holder is preferably made of metal and formed by investment casting or the like.

A sealing means is provided for sealing the piston rod 70 and, hence, sealing the cylinder 34 of the cylinder member 33 below the piston 69 from the cylinder 21 of the cylinder sleeve 20 above the piston 68. This sealing means includes a cupshaped member 86 which abuts against the shoulder 35 in the inner part 32 of the cylinder member and is held in place by the valve disc 47 which engages a shoulder on the cup-shaped member 86. The cup-shaped member 86 is sealed in the inner part 32 of the cylinder member by an O-ring 87. A gland 88 caries a pair of O-rings 89 which engage the piston rod 70 of the differential piston unit and also the cup-shaped member 86, the gland 88 being held in place by a snapring 91 snapped into a groove in the cup-shaped member 86. The cup shaped member 86 and the gland 88 are preferably molded from a suitable rigid synthetic plastic material. The O-rings 89 in addition to sealing the piston rod 70 also form a seal between the cup-shaped member 86 and the gland 88.

The nail-driving blade 94, as shown more particularly in FIG. 8, extends through slots 96 in the two-part holder 77 and it is provided with a T-shaped portion at its upper end. The bottom sides of the T-shaped portion 95 engage shoulders 97 in the holder 77 so that when the holder 77 is moved upwardly,,the blade 94 is retracted therewith. A backup plate 98 is arranged between the top side of the T-shaped portion 95 of the blade and the head 79 of the screw 81, the backup plate 98 having flats mating with the flats 78 in the holder. Thus, as the differential piston unit 67 is moved downwardly, the backup plate 98 in the holder 77 engages the top of the T-shaped portion 95 of the blade 94 for advancing the blade 94. Preferably, the blade 94 and the backup plate are formed of metal, such as, steel stampings, or the like.

A handle cover 100 encompasses the upper inner portion 33 of the cylinder member and it is secured to the cover 50 by means of screws 101. The handle cover 100 is provided with radial slots 102 for venting the top of the cylinder 34 of the cylinder member above the upper small diameter piston 69 and for completing the vent passage from above the upwardly facing annular valve seat 48. The handle cover 100 is preferably provided with a lubricant fitting 103 for supplying lubricant to the cylinder 34 of the cylinder member 33. It is also here noted that the lubricant fitting 103 is not subject to air under pressure. The handle cover 100 is useful in manipulating the nailing machine as it is being used. The handle cover may be made of any suitable material but preferably it is made from a suitable rigid synthetic plastic material.

A foot plate 105 is secured by screws 106 to the bottom of the hollow housing 11 below the lower cylinder portion 17 thereof and, hence, below the differential piston unit 67. The foot plate 105 carries an annular resilient rubber bumper 107 about the nail-driving blade 94, the rubber bumper 107 being secured in place by a ring 108 having a plurality of outwardly extending fingers which are clamped between the foot plate 105 and a ring 109 in the housing. The foot plate 105 is provided with a plurality of circumferentially arranged slots 110 which in addition to the central opening in the foot plate provide air passages for venting air to atmosphere from beneath the large diameter piston 68 of the differential piston unit. Thus, as the differential piston unit 67 is reciprocated, air is directed around the annular rubber bumper 107 as well as through the center thereof so as to provide maximum cooling of the rubber bumper 107 to dissipate heat therefrom which is generated by the lower large diameter piston 68 engaging the rubber bumper 107 as the nailing blade 94 is advanced.

The foot plate 105 also has a pair of depending flanges 112 and flanges 113 extending laterally therefrom. A magazine 114 extends between the flanges 112 and has flanges 115 engaging the flanges 113 for securing the magazine to the foot plate. The magazine 114 also has a bracket portion 115 which is secured to an extension 116 from the handle portion 12 of the housing 11 for providing further support for the magazine 114. The magazine 114 is channel shaped for receiving and guiding a strip of nails inserted therein, the heads of the nails extending over a guiding edge 117 on one of the legs of the magazine. When a strip of nails, adhesively secured together, is inserted in the magazine, it is maintained therein by a guide flange 118 arranged above the heads of the nails. A handle 119 is provided for manually manipulating a feed device 120 which is urged forwardly by a spring 121 and a locking arrangement 122 is provided for locking the feed device 120 in its retracted position as shown in FIG. 1. When nails are inserted in the magazine 114 and the locking device 122 released, the spring 121 operates through the feed device 120 for advancing the nails between the legs 112 of the foot plate 105.

A nail guide plate 125 and a blade guide plate 126 are I secured to the flanges 113 of the foot plate 105 by means of screws and nuts 127, these same screws and nuts 127 securing the flanges 115 of the magazine 114 in place. The nail guide plate has an opening therein corresponding to the shape ofthe nails to be driven and this opening operates accurately to guide the nails as they are advanced into the blade guide plate 126 below the blade 94. The blade guide plate 126 has a channel 128 therein for guiding the blade 94 as it is advanced and retracted by the differential piston unit 67. When the blade 94 is retracted the end nail of a strip of nails is fed into the channel 128 in the blade guide plate 126 and when the blade 94 is advanced, it drives the nail into the object to be nailed.

The blade guide plate 126 also has a pair of channels 129 which slidably receive a pair of pins 130 normally project below the nail and blade guide plates 12S and 126. These pins 130 are provided with shoulders which underlie fingers 131 on a lever 132 which is pivoted at 133 to the foot plate 105. The pins 130 and the lever 132 are normally in the down position as illustrated in FIGS. 1 to 4. However, when the foot plate of the nailing machine is placed against an object to be nailed, the pins 130 are pushed upwardly to cause the pivoted lever 132 to swing upwardly to the position illustrated in FIG. 9.

Below the handle portion 12 the housing 11 is provided with a boss 136 which has a downwardly facing cylindrical chamber 137. As shown more clearly in FIGS. 17 and 18, this boss 136 is provided with a drilled passage 138 extending from the internal cavity of the hollow housing 11 and which is closed at its bottom end by a plug 140. Another drilled passage 139 communicating with the passage 138 enters into the cylindrical chamber 137, the other end of the passage 139 being closed by a plug 141. The passages 138, 139 supply air under pressure into the cylindrical chamber 137 from the cavity 15 of the hollow housing 11. The boss 136 also has a vertical drilled passage 141 extending from the intermediate cylindrical cavity 16 in the housing member 11 below the piston flange 30 of the cylinder sleeve 20, this passage 141 being closed at its bottom end by a plug 143. A drilled passage 142 connects the passage 141 to the interior of the cylindrical chamber 137 at a point below the point where the passage 139 communicates with the cylindrical chamber 137. Thus, the passages 141, 142 connect the intermediate cylindrical portion 16 of the hollow housing 11 below the piston flange 30 of the cylinder sleeve with the cylindrical chamber 137.

A control valve assembly, as shown more clearly in FIGS. 19 and 20, is arranged within the cylindrical chamber 137, it including a valve housing 146 having a closure disc 147 secured thereto by screws or the like, not shown. The valve housing 146 and closure disc 147 may be formed of any suitable material but preferably they are molded from a suitable rigid synthetic plastic material. The control valve housing is provided with an external annular groove 148 which communicates with the passage 139, 138 leading from the cavity 15 in the hollow housing 11 so that air under pressure is supplied to this annular groove 148. The exterior ofthe valve housing 146 is also provided with an annular groove 149 which communicates with the passage 142, 141 so that this annular groove 149 is in communication with the intermediate cylindrical cavity 16 in the hollow housing 11. These annular grooves 148 and 149 are sealed in the cylindrical chamber 137 by 0 rings 150,151 and 152.

The control valve housing 146 is provided with a first bore therethrough including an upper large diameter bore 154, an intermediate diameter bore and a lower smaller diameter bore 156. I-Ioles 157 and 158 in the control valve housing 146 and the closure disc 147 communicate with the lower smaller bore 156. The upper bore 154 is sealed with respect to the cylindrical chamber 137 by an Oring 159 and the holes 157 and 158 are sealed by an O ring 160. A hole 162 communicates the upper large diameter bore 154 with the annular groove 148 and a hole 163 communicates the intermediate diameter bore 155 with the annular groove 149. A shoulder 164 forming a valve seat is arranged between the intermediate diameter bore 155 and the smaller diameter bore 156.

Arranged within the intermediate diameter bore 155 of the valve housing 146 is a valve 165 which has a valve stem 166 extending downwardly through the small diameter bore 156, the holes 157 and 158 and a hole in the foot plate 105 to a point below the foot plate 105 so as to be engageable by the pivoted lever 132. The O-ring which seals the holes 157 and 158 also seals the valve stem 166. A compression spring 167 within the large diameter bore 154 resiliently urges the valve downwardly. The valve 165 is provided with a central bore 168 which is connected by a plurality of radial passages 169 to an annular groove 170 in the exterior of the valve 165. This annular groove 170 is in communication with the passage 163 in the valve housing 146 when the valve 165 is in its normal down position as illustrated in FIG. 19. An O-ring 171 seals the valve 169 in the intermediate bore 155 between the passages 162 and 163. The bottom annular portion of the valve 169 is provided with an O-ring 172 which is held in place by friction and suction in an annular groove in the valve and which seats against the annular shoulder 164 when the valve is in its normal lowered position as illustrated in FIG. 19.

The valve housing 146 is also provided with a second bore therethrough, the second bore including an upper small diameter bore 175, a lower large diameter bore 176 and an intermediate conical portion 177. A passage 178 connects the lower small diameter bore 156 of the first bore to the lower large diameter bore 176 of the second bore. The large diameter bore 176 is sealed by an O-ring 179 arranged between the valve housing 146 and the closure disc 147. A second valve 180 is located in the lower large diameter bore 176 and it has a conical surface adapted to engage the conical surface 177 between the bores and 176. A compression spring 181 resiliently urges the valve into engagement with its conical seat 177. A fluted stem 182 extends upwardly through the small diameter bore 175 and a hole in the boss 136. A trigger 184 is pivoted at 185 to the handle portion 12 of the nailing machine is operable to move the valve 180 downwardly against the action of the spring 181 when it is depressed, as illustrated in FIG. 20. The valve 165 and its downwardly depending stem 166 and the upwardly extending fluted stem 182 are preferably molded from a suitable rigid synthetic plastic material, while the valve 180 is preferably molded from a suitable resilient synthetic rubber or rubberlike plastic material, such as, for example, buna rubber or the like.

When the valve 169 is in its normal bottom position, as illustrated in FIG, 19, air under pressure from the cavity 15 in the housing 11 is delivered through the passages I38, 139, annular groove 137, passages 162, 168 and 169, annular groove 170, passage 163, annular groove 149 and passages 142 and 141 to the intermediate cylindrical chamber 16 in the housing 11 below the piston flange 30 on the cylinder sleeve 20. As a result, the cylinder sleeve 20 is in its raised position as illustrated in FIG. 4 and the differential piston unit 67 is also in its raised position. In this latter connection the annular upwardly facing valve seat 23 is engaging the valve ring 60 and the valve ring 60 is disengaged from the stationary upwardly facing valve seat 48. With these valve means in these positions as illustrated in FIG. 4, the supply of air pressure in the upper cavity of the housing 11 is sealed from above the lower large diameter piston 68 by the annular valve seat 23 engaging the valve ring 60. Air above the large diameter piston 68 is vented to atmosphere around the upwardly facing annular valve seat 48 through the radial slots 41, passages 40, 36, annular groove 37, hole 51 in the cover plate 50 and passages 102 in the handle cover 100. Air under pressure from the cavity 15 of the housing 11 is transmitted below the upper small diameter piston 69 through slots 64 in the valve sleeve 56, annular groove 42 and passages 43 and 44 into the cylinder 34 of the upper cylinder member 33. Thus, the differential piston is held in its raised position as illustrated in FIG. 4.

When the foot plate of the nailing machine is placed against an object to be nailed, the pins 130 pivot the lever 132 upwardly about its pivot 133 as illustrated in FIGS. 9 and 20. This pivoting of the lever 132 raises the valve 169 through its valve stem 166 to its second or upper position against the action of the spring 167 as illustrated in FIGS. 9 and 20. When this occurs, the annular groove 170 of the valve 165 is moved upwardly out of registry with the passage 163 so as to interrupt the supply of air under pressure from the upper cavity 16 of the housing 11 to below the piston flange 30 of the cylinder sleeve 20. The passage 163 and, hence, the intermediate cylinder 16 below the piston flange 22 of the cylinder sleeve 20 is connected through the intermediate diameter bore 155,

-' small diameter bore 156 and passage 178 to the large diameter bore 176 for the second valve. However, since the second valve 180 is engaging its seat 177 the intermediate cylinder 16 below the piston flange of the cylinder sleeve 20 is not vented to atmosphereand the cylinder sleeve 20, valve sleeve 56 and the differential piston 67. remain in their upper positions as illustrated in FIG. 4.

However, when the trigger 184 is depressed, the fluted stem 182 presses the valve 180 downwardly against the action of the spring 181 to connect the large diameter bore 176 past the valve 180 and through the fluted stem 182 to atmosphere. As a result, when the valves 165 and 180 are both in their second positions as illustrated in FIGS. 9 and 20, the intermediate cylinder 16 of the housing 11 below-the piston flange 30 is vented to atmosphere through passages 141, 142 annular groove 149, passage 163, intermediate diameter bore 155, small diameter bore 156, passage 178, large diameter bore 176, small diameter bore 175 and fluted stem 182. As a result, air under pressure in the cavity 15 of the housing 11 acts upon the piston shoulder 58 of the valve sleeve 56 to move the valve sleeve 56 and the cylinder sleeve 20 downwardly for causing the valve ring 60 to engage the upwardly facing annular valve seat 48 to interrupt the venting to atmosphere of the cylinder 21 above the lower large diameter piston 68 of the differential piston unit 67. Also, when this occurs, air under pressure in the cavity 15 of the housing 11 acts on the piston shoulder 22 of the cylinder sleeve 20 to move it downwardly to the position shown in FIG. 9. When this occurs, air under pressure from the cavity 15 in the housing 11 is supplied over the annular valve seat 23 to the cylinder 21 above the large diameter piston 68 to drive the differential piston 68 downwardly against the action of the air under pressure below the upper small diameter piston 69 of the differential piston unit. The downward movement of the differential piston unit 67 advances the nailing blade 94 to drive the nail into the object to be nailed.

When the foot plate is thereafter removed from the work to be nailed and the trigger 184 is released, the first and second valves 165 and 180 are returned by their respective springs 167 and 181 to the positions shown in FIGS. 4 and 19 and the differential piston unit 67 is moved to its raised position in the manner previously described above. When the differential piston unit 67 is so raised, another nail is advanced from the magazine 114 through the contoured aperture in the nail guide plate below the nail-driving blade 94 to condition the nailing machine for its next cycle ofoperation.

The valving means including the upwardly facing annular valve seats 23 and 48 on the cylinder sleeve 20 and the cylinder member 32, 39 and the downwardly facing annular valve ring 60 on the valve sleeve 56 provide for rapid control for large volumes of air, air above the lower large diameter piston 68 being rapidly vented to atmosphere and air under pressure being rapidly supplied to the upper side of the lower large diameter piston 68. Furthermore, since the valve seat 23 engages the valve ring 60 before the valve ring 60 disengages the valve seat 48 and since the valve ring 60 engages the valve seat 48 before the valve seat 23 disengages the valve ring 60, positive valving action is assured and there is no escape of air under pressure to the atmosphere. As a result, maximum nailing forces with minimum expenditure of air are assured.

The control valve means including the control valves and in the valve housing 146 provide a simple and accu rate control for the movement of the cylinder sleeve 20 and the valve sleeve 56 so that the nailing machine is operated in a safe and foolproof manner. The disclosed means including the holder 77 for securing the nail-driving blade 94 to the differential piston unit 67 provides a hard driving connection for the nail-driving blade but, yet, permits relative movement between the blade and the holder so that there is no binding of the blade as it is retracted and advanced in its groove 128 formed in the guide plate 126 carried by the foot plate 105.

By molding from suitable rigid synthetic plastic materials, such as, for example, NORYL 731-701 or the like, the vari ous parts as described above may be accurately manufactured and machining of the parts is maintained at a minimum. Also, the various parts of the nailing machine may be readily and easily assembled with minimum man hours required. As a result, the nailing machine of this invention may be inexpensively manufactured.

While for purposes of illustration, one preferred form of this invention has been disclosed, other forms of this invention may become apparent to those skilled in the art and, therefore, this invention is to be limited only by the scope of the appended claims.

lelaim:

l. A pneumatically operated nailing machine comprising a reciprocatable blade for driving nails when advanced, a reciprocatable differential piston unit having a lower large diameter piston and an upper small diameter piston connected by a piston rod, means securing the blade to the differential piston unit to be advanced and retracted thereby, a reciprocatable cylinder sleeve having a cylinder reciprocatingly receiving the lower large diameter piston of the differential piston unit, a cylinder member having a cylinder reciprocatingly receiving the upper small diameter piston of the differential piston unit, sealing means for the piston rod of the differential piston unit for sealing the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston, valving means including an annular upwardly facing valve seat on the cylinder sleeve, a stationary annular upwardly facing valve seat adjacent the valve seat on the cylinder sleeve, and a reciprocatable valve sleeve having a downwardly facing annular valve ring adapted to engage the stationary upwardly facing valve seat and to be engaged by the upwardly facing valve seat on the cylinder sleeve, means including passageways for supplying air under pressure beneath the upper small diameter piston and for venting to atmosphere air above the lower large diameter piston to drive the differential piston unit upwardly and retract the blade when the cylinder sleeve is moved upwardly to engage its annular upwardly facing valve seat with the annular downwardly facing valve ring of the valve sleeve and to disengage the annular downwardly facing valve ring of the valve sleeve from the stationary annular upwardly facing valve seat, and for interrupting the venting of air to atmosphere from above the large diameter piston and for supplying air under pressure above the large diameter piston to drive the differential piston downwardly and advance the blade when the cylinder sleeve is moved downwardly to engage the annular downwardly facing valve ring of the valve sleeve with the stationary annular upwardly facing valve seat and to disengage the annular upwardly facing valve sleeve of the cylinder sleeve from the annular downwardly facing valve ring of the valve sleeve, and means including control valve means for selectively moving said cylinder sleeve and valve sleeve upwardly and downwardly.

2. A nailing machine as defined in claim 1 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that the cylinder sleeve is moved downwardly to advance the blade only when both valves are moved to their second positions.

3. A nailing machine as defined in claim 1 wherein said means for selectively moving said cylinder sleeve upwardly and downwardly also includes a piston flange on said cylinder sleeve, and said control valve means selectively supplies air under pressure to and vents air from said piston flange for moving said cylinder sleeve upwardly and downwardly, respectively.

4. A nailing machine as defined in claim 3 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that air from said piston flange is vented to atmosphere to move the cylinder sleeve downwardly and advance the blade when both valves are moved to their second positions.

5. A nailing machine as defined in claim 1 including a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, an annular rubber bumper carried by the foot plate around the reciprocatable blade to be engaged by the lower large diameter piston of the differential piston unit when the latter is moved downwardly, and vent passages in the foot plate about the annular rubber bumper for directing air from below the differential piston unit, when the latter is moved downwardly, about the annular rubber bumper for cooling the same.

6. A nailing machine as defined in claim 1 including a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, a nail guide plate carried by the foot plate for guiding the reciprocatable blade and a nail to be driven thereby, and a magazine carried by the foot plate for feeding nails to the nail guide plate.

7. A nailing machine as defined in claim 1 wherein the upper end of said reciprocatable blade is T-shapcd and said means for securing the blade to the lower end of the differential piston unit includes a two-part separable holder secured to the lower end of the differential piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the under sides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T-shaped portion of said blade.

8. A pneumatically operated nailing machine comprising a hollow housing supplied with air under pressure, a reciprocatable blade extending through the bottom of the housing for driving nails when advanced, a reciprocatable differential piston unit in the housing having a lower large diameter piston and an upper small diameter piston connected by a piston rod, means securing the blade to the lower end of the differential piston unit to be advanced and retracted thereby, a cylinder sleeve reciprocatably mounted in the housing and having a cylinder reciprocatingly receiving the lower large diameter piston of the differential piston unit, said cylinder sleeve having at its upper end an upwardly facing annular valve seat and an annular piston shoulder of small area therearound subject to the air under pressure in the housing and having intermediate its ends an annular piston flange of large area therearound, a cylinder member in the housing hav ing a cylinder reciprocatingly receiving the upper small diameter piston ofthe differential piston unit, said cylinder member having sealing means for the piston rod of the differential piston unit for sealing the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston and having an upwardly facing annular valve seat of smaller diameter than the annular valve seat at the upper end of the cylinder sleeve and located adjacent thereto and radially spaced inwardly therefrom, a valve sleeve reciprocatingly carried by the cylinder member and having a downwardly facing annular valve ring engageable with said upwardly facing annular valve seats ofsaid cylinder sleeve and cylinder member and having an annular piston shoulder subject to the air under pressure in the housing, said cylinder member including passageways for venting to atmosphere the upwardly facing annular valve seat thereof and the cylinder thereof above the upper small diameter piston of the differential piston unit, said housing having passageways for venting to atmosphere the cylinder of the cylinder sleeve below the lower large diameter piston of the differential piston unit, said cylinder member having passageways for supplying air under pressure from the hollow housing to the cylinder thereof below the upper small diameter piston of the differential piston unit, means including control valve means in one condition for supplying air under pressure from the housing below the annular piston flange of the cylinder sleeve for moving the same upwardly to cause the annular valve seat thereof to engage the annular valve ring of the valve sleeve and to move the valve sleeve upwardly to disengage the annular valve ring thereof from the annular valve seat of the cylinder member for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the air under pressure in the housing and for venting the same to atmosphere, whereby the air under pressure in the cylinder of the cylinder member below the upper small diameter piston of the differential piston unit moves the same upwardly to retract the nail-driving blade, said means including said control valve means also being operative in another condition for venting to atmosphere air from below the annular piston flange of the cylinder sleeve for allowing the air under pressure in the housing acting on the annular piston shoulder of the valve sleeve and the annular piston shoulder of the cylinder sleeve to move the same downwardly, to cause the annular valve ring of the valve sleeve to engage the annular valve seat ofthe cylinder member and to disengage the annular valve seat of the cylinder sleeve from the annular valvc ring of the valve sleeve for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the atmosphere and supplying air under pressure thereto from the housing, whereby the air under pressure in the cylinder of the cylinder sleeve above the large diameter piston of the differential piston unit overcomes the force of the air under pressure in the cylinder of the cylinder member below the small diameter piston of the differential piston unit and moves the same downwardly to advance the nail-driving blade.

9. A nailing machine as defined in claim 8 wherein said hollow housing has an upper portion of large transverse dimensions which is supplied with the air under pressure, a lower cylindrical portion of small transverse dimension which slidably mounts the lower part of the cylinder sleeve, and an intermediate portion of intermediate transverse dimension which forms a cylinder for receiving the annular piston flange of the cylinder sleeve, said annular piston flange has packing for slidably sealing the same to said intermediate portion of the housing, and said housing carries upper and lower packings slidably receiving the cylinder sleeve for sealing the upper portion of the housing from the cylinder forming intermediate portion of the housing and for sealing the cylinder forming intermediate portion of the housing from the lower portion of the housing.

10. A nailing machine as defined in claim 8 wherein said upper small diameter piston and said lower large diameter piston of the differential piston unit have packing for slidably sealing the same in the cylinder of the cylinder member and in the cylinder of the cylinder sleeve.

11. A nailing machine as defined in claim 9 wherein said upper small diameter piston and said lower large diameter piston of the differential piston unit have packing for slidably sealing the same in the cylinder of the cylinder member.

12. A nailing machine as defined in claim 9 wherein said packings are V-type packings.

13. A nailing machine as defined in claim 10 wherein said packings are V-type packings.

14. A nailing machine as defined in claim 9 including a lubricant fitting in the intermediate portion of the housing below the upper packing and above the annular piston flange packing, and a lubricant fitting in the lower portion of the housing below the lower packing, said fittings being free from air under pressure.

15. A nailing machine as defined in claim 8 wherein said hollow housing includes a top cover secured to the remainder of the housing, said cylinder member is secured to the underside of said cover within the housing, and said cylinder of said cylinder member extends above the housing and the cover.

16. A nailing machine as defined in claim wherein said housing includes a hollow handle cover secured to said cover about the cylinder of said cylinder member, and said hollow handle cover has passageways for venting to atmosphere the passageways in the cylinder member which vent the u wardly facing valve seat thereof and the cylinder thereof above the upper small diameter piston of the differential piston unit.

17. A nailing machine as defined in claim 16 wherein said hollow handle cover includes a lubricating fitting above the upper small diameter piston of the differential piston unit, said fitting being free from air under pressure.

18. A nailing machine as defined in claim 8 wherein said housing includes a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, an annular rubber bumper is carried by the foot plate around the reciprocatable blade to be engaged by the lower large diameter piston of the differential piston unit when the latter is moved downwardly, the foot plate is provided with vent passages about the annular rubber bumper for directing the air, which is vented to atmosphere from below the differential piston unit when the latter is moved downwardly, about the annular rubber bumper for cooling the same.

1 9. A nailing machine as defined in claim 8 wherein said housing includes a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, a nail guide plate is carried by the foot plate for guiding the reciprocatable blade and a nail to be driven thereby, and a magazine is carried by the foot plate for feeding nails to the nail guide plate.

20. A nailing machine as defined in claim 8 wherein the upper end of said reciprocatable blade is T-shaped and said means for securing the blade to the lower end of the differential piston unit includes a two-part separable holder secured to the lower end of the differential piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the under sides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T-shaped portion of said blade.

21. A nailing machine as defined in claim 8 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that air'from below the piston flange of the cylinder sleeve is vented to atmosphere to move the cylinder sleeve downwardly and advance the naildriving blade when both valves are moved to their second positions.

22. A nailing machine as defined in claim 1 wherein said valve sleeve has an annular groove with a vent passage extending from the bottom of the groove, said downwardly facing annular valve ring is resilient and has annular ridges on the sides thereof, said resilient annular valve ring is forced into said annular groove with the air behind said ring being vented through the vent passage, and a plug is inserted in the vent passage to close the same whereby the resilient annular ring is secured in the annular groove by vacuum as well as by its resiliency.

23. A nailing machine as defined in claim 8 wherein said valve sleeve has an annular groove with a vent passage extending from the bottom of the groove, said downwardly facing annular valve ring is resilient and has annular ridges on the sides thereof, said resilient annular valve ring is forced into said annular groove with the air behind said ring being vented through the vent passage, and a plug is inserted in the vent passage to close the same whereby the resilient annular ring is secured in the annular groove by vacuum as well as by its resiliency.

24. A nailing machine as defined in claim 8 wherein said cylinder member is a two-part telescopically arranged member, the inner part includes the cylinder for the upper small diameter piston of the differential piston unit and carries the sealing means for the piston rod of the differential piston unit, the outer part slidably carries the valve sleeve, and the inner part and the outer part have mating longitudinal grooves forming the passageways for venting to atmosphere the upwardly facing annular valve seat of the cylinder member.

25. A nailing machine as defined in claim 24 wherein said inner part and outer part of said cylinder member have registered holes forming the passageways for supplying air under pressure from the hollow housing to the cylinder below the upper small diameter of the differential piston unit.

26. A nailing machine as defined in claim 1 wherein said cylinder sleeve, cylinder member and valve sleeve are molded from a suitable rigid synthetic plastic material.

27. A nailing machine as defined in claim 8 wherein said cylinder sleeve, cylinder member and valve sleeve are molded from a suitable rigid synthetic plastic material. V

28. A nailing machine as defined in claim 24 wherein the inner and outer parts of the cylinder member are molded from a suitable synthetic plastic material.

29. A nailing machine as defined in claim 2 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.

30. A nailing machine as defined in claim 4 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the piston flange on said cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.

St. A nailing machine as defined in claim 8 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the piston flange on said cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.

32. A pneumatically operated nailing machine including, a housing, a reciprocatable blade for driving nails when advanced, a reciprocatable air-operated piston unit in the housing connected to the blade for retracting and advancing the blade as the piston unit is raised and lowered, and means including control valve means for controlling the raising and lowering of the piston unit, the improvement wherein said means including said control valve means comprises a valve housing in the nailing machine housing having first and second bores, a first valve in the first bore having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed, a second valve in the second bore having a normal position and movable to a second position when a control trigger is manually depressed, said valve housing having a first passage connecting the first valve to a source of air under pressure, a second passage connecting the first valve to the air-operated piston unit, a third passage connecting the first valve to the second valve, and a fourth passage connecting the second valve to atmosphere, the arrangement being such that the air-operated piston unit is moved downwardly to advance the nail-driving blade only when both valves are moved to their second positions.

33. A nailing machine as defined in claim 32 wherein said valve housing has sealing means for sealing said first and second bores therein and said first and second passages.

34. A nailing machine as defined in claim 32 wherein said valve housing is molded from a suitable rigid synthetic plastic material.

35. A nailing machine as defined in claim 32 wherein said first valve is molded from a suitable rigid synthetic plastic material.

36. A nailing machine as defined in claim 32 wherein said second valve is molded from a suitable resilient synthetic rubber or rubberlike plastic material.

37. A pneumatically operated nailing machine including a reciprocatable blade for driving nails when advanced, a reciprocatable air-operated piston unit, and means securing the blade to the piston unit to be advanced and retracted thereby, the improvement wherein the upper end of said reciprocatable blade is T-shaped, and said means for securing the blade to the piston unit includes a two-part separable holder secured to the piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the undersides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T- shaped portion of said blade when the piston unit advances the blade for driving nails. 

1. A pneumatically operated nailing machine comprising a reciprocatable blade for driving nails when advanced, a reciprocatable differential piston unit having a lower large diameter piston and an upper small diameter piston connected by a piston rod, means securing the blade to the differential piston unit to be advanced and retracted thereby, a reciprocatable cylinder sleeve having a cylinder reciprocatingly receiving the lower large diameter piston of the differential piSton unit, a cylinder member having a cylinder reciprocatingly receiving the upper small diameter piston of the differential piston unit, sealing means for the piston rod of the differential piston unit for sealing the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston, valving means including an annular upwardly facing valve seat on the cylinder sleeve, a stationary annular upwardly facing valve seat adjacent the valve seat on the cylinder sleeve, and a reciprocatable valve sleeve having a downwardly facing annular valve ring adapted to engage the stationary upwardly facing valve seat and to be engaged by the upwardly facing valve seat on the cylinder sleeve, means including passageways for supplying air under pressure beneath the upper small diameter piston and for venting to atmosphere air above the lower large diameter piston to drive the differential piston unit upwardly and retract the blade when the cylinder sleeve is moved upwardly to engage its annular upwardly facing valve seat with the annular downwardly facing valve ring of the valve sleeve and to disengage the annular downwardly facing valve ring of the valve sleeve from the stationary annular upwardly facing valve seat, and for interrupting the venting of air to atmosphere from above the large diameter piston and for supplying air under pressure above the large diameter piston to drive the differential piston downwardly and advance the blade when the cylinder sleeve is moved downwardly to engage the annular downwardly facing valve ring of the valve sleeve with the stationary annular upwardly facing valve seat and to disengage the annular upwardly facing valve sleeve of the cylinder sleeve from the annular downwardly facing valve ring of the valve sleeve, and means including control valve means for selectively moving said cylinder sleeve and valve sleeve upwardly and downwardly.
 2. A nailing machine as defined in claim 1 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that the cylinder sleeve is moved downwardly to advance the blade only when both valves are moved to their second positions.
 3. A nailing machine as defined in claim 1 wherein said means for selectively moving said cylinder sleeve upwardly and downwardly also includes a piston flange on said cylinder sleeve, and said control valve means selectively supplies air under pressure to and vents air from said piston flange for moving said cylinder sleeve upwardly and downwardly, respectively.
 4. A nailing machine as defined in claim 3 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that air from said piston flange is vented to atmosphere to move the cylinder sleeve downwardly and advance the blade when both valves are moved to their second positions.
 5. A nailing machine as defined in claim 1 including a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, an annular rubber bumper carried by the foot plate around the reciprocatable blade to be engaged by the lower large diameter piston of the differential piston unit when the latter is moved downwardly, and vent passages in the foot plate about the annular rubber bumper for directing air from below the differential piston unit, when the latter is moved downwardly, about the annular rubber bumper for cooling the same.
 6. A nailing machine as defined iN claim 1 including a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, a nail guide plate carried by the foot plate for guiding the reciprocatable blade and a nail to be driven thereby, and a magazine carried by the foot plate for feeding nails to the nail guide plate.
 7. A nailing machine as defined in claim 1 wherein the upper end of said reciprocatable blade is T-shaped and said means for securing the blade to the lower end of the differential piston unit includes a two-part separable holder secured to the lower end of the differential piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the under sides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T-shaped portion of said blade.
 8. A pneumatically operated nailing machine comprising a hollow housing supplied with air under pressure, a reciprocatable blade extending through the bottom of the housing for driving nails when advanced, a reciprocatable differential piston unit in the housing having a lower large diameter piston and an upper small diameter piston connected by a piston rod, means securing the blade to the lower end of the differential piston unit to be advanced and retracted thereby, a cylinder sleeve reciprocatably mounted in the housing and having a cylinder reciprocatingly receiving the lower large diameter piston of the differential piston unit, said cylinder sleeve having at its upper end an upwardly facing annular valve seat and an annular piston shoulder of small area therearound subject to the air under pressure in the housing and having intermediate its ends an annular piston flange of large area therearound, a cylinder member in the housing having a cylinder reciprocatingly receiving the upper small diameter piston of the differential piston unit, said cylinder member having sealing means for the piston rod of the differential piston unit for sealing the cylinder for the lower large diameter piston from the cylinder for the upper small diameter piston and having an upwardly facing annular valve seat of smaller diameter than the annular valve seat at the upper end of the cylinder sleeve and located adjacent thereto and radially spaced inwardly therefrom, a valve sleeve reciprocatingly carried by the cylinder member and having a downwardly facing annular valve ring engageable with said upwardly facing annular valve seats of said cylinder sleeve and cylinder member and having an annular piston shoulder subject to the air under pressure in the housing, said cylinder member including passageways for venting to atmosphere the upwardly facing annular valve seat thereof and the cylinder thereof above the upper small diameter piston of the differential piston unit, said housing having passageways for venting to atmosphere the cylinder of the cylinder sleeve below the lower large diameter piston of the differential piston unit, said cylinder member having passageways for supplying air under pressure from the hollow housing to the cylinder thereof below the upper small diameter piston of the differential piston unit, means including control valve means in one condition for supplying air under pressure from the housing below the annular piston flange of the cylinder sleeve for moving the same upwardly to cause the annular valve seat thereof to engage the annular valve ring of the valve sleeve and to move the valve sleeve upwardly to disengage the annular valve ring thereof from the annular valve seat of the cylinder member for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the air under pressure in the housing and for venting the same to atmosphere, whereby the air under pressure in the cylinder of the cylinder member below the upper small diameter piston of the differential piston unit moves the same upwardly to retract tHe nail-driving blade, said means including said control valve means also being operative in another condition for venting to atmosphere air from below the annular piston flange of the cylinder sleeve for allowing the air under pressure in the housing acting on the annular piston shoulder of the valve sleeve and the annular piston shoulder of the cylinder sleeve to move the same downwardly, to cause the annular valve ring of the valve sleeve to engage the annular valve seat of the cylinder member and to disengage the annular valve seat of the cylinder sleeve from the annular valve ring of the valve sleeve for sealing the cylinder of the cylinder sleeve above the lower large diameter piston of the differential piston unit from the atmosphere and supplying air under pressure thereto from the housing, whereby the air under pressure in the cylinder of the cylinder sleeve above the large diameter piston of the differential piston unit overcomes the force of the air under pressure in the cylinder of the cylinder member below the small diameter piston of the differential piston unit and moves the same downwardly to advance the nail-driving blade.
 9. A nailing machine as defined in claim 8 wherein said hollow housing has an upper portion of large transverse dimensions which is supplied with the air under pressure, a lower cylindrical portion of small transverse dimension which slidably mounts the lower part of the cylinder sleeve, and an intermediate portion of intermediate transverse dimension which forms a cylinder for receiving the annular piston flange of the cylinder sleeve, said annular piston flange has packing for slidably sealing the same to said intermediate portion of the housing, and said housing carries upper and lower packings slidably receiving the cylinder sleeve for sealing the upper portion of the housing from the cylinder forming intermediate portion of the housing and for sealing the cylinder forming intermediate portion of the housing from the lower portion of the housing.
 10. A nailing machine as defined in claim 8 wherein said upper small diameter piston and said lower large diameter piston of the differential piston unit have packing for slidably sealing the same in the cylinder of the cylinder member and in the cylinder of the cylinder sleeve.
 11. A nailing machine as defined in claim 9 wherein said upper small diameter piston and said lower large diameter piston of the differential piston unit have packing for slidably sealing the same in the cylinder of the cylinder member.
 12. A nailing machine as defined in claim 9 wherein said packings are V-type packings.
 13. A nailing machine as defined in claim 10 wherein said packings are V-type packings.
 14. A nailing machine as defined in claim 9 including a lubricant fitting in the intermediate portion of the housing below the upper packing and above the annular piston flange packing, and a lubricant fitting in the lower portion of the housing below the lower packing, said fittings being free from air under pressure.
 15. A nailing machine as defined in claim 8 wherein said hollow housing includes a top cover secured to the remainder of the housing, said cylinder member is secured to the underside of said cover within the housing, and said cylinder of said cylinder member extends above the housing and the cover.
 16. A nailing machine as defined in claim 15 wherein said housing includes a hollow handle cover secured to said cover about the cylinder of said cylinder member, and said hollow handle cover has passageways for venting to atmosphere the passageways in the cylinder member which vent the upwardly facing valve seat thereof and the cylinder thereof above the upper small diameter piston of the differential piston unit.
 17. A nailing machine as defined in claim 16 wherein said hollow handle cover includes a lubricating fitting above the upper small diameter piston of the differential piston unit, said fitting being free from air under pressure.
 18. A nailing machiNe as defined in claim 8 wherein said housing includes a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, an annular rubber bumper is carried by the foot plate around the reciprocatable blade to be engaged by the lower large diameter piston of the differential piston unit when the latter is moved downwardly, the foot plate is provided with vent passages about the annular rubber bumper for directing the air, which is vented to atmosphere from below the differential piston unit when the latter is moved downwardly, about the annular rubber bumper for cooling the same.
 19. A nailing machine as defined in claim 8 wherein said housing includes a foot plate below the cylinder sleeve and the lower large diameter piston of the differential piston unit and through which the reciprocatable blade extends, a nail guide plate is carried by the foot plate for guiding the reciprocatable blade and a nail to be driven thereby, and a magazine is carried by the foot plate for feeding nails to the nail guide plate.
 20. A nailing machine as defined in claim 8 wherein the upper end of said reciprocatable blade is T-shaped and said means for securing the blade to the lower end of the differential piston unit includes a two-part separable holder secured to the lower end of the differential piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the under sides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T-shaped portion of said blade.
 21. A nailing machine as defined in claim 8 wherein said means including control valve means includes a first valve having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed and a second valve having a normal position and movable to a second position when a control trigger is manually depressed, the arrangement being such that air from below the piston flange of the cylinder sleeve is vented to atmosphere to move the cylinder sleeve downwardly and advance the nail-driving blade when both valves are moved to their second positions.
 22. A nailing machine as defined in claim 1 wherein said valve sleeve has an annular groove with a vent passage extending from the bottom of the groove, said downwardly facing annular valve ring is resilient and has annular ridges on the sides thereof, said resilient annular valve ring is forced into said annular groove with the air behind said ring being vented through the vent passage, and a plug is inserted in the vent passage to close the same whereby the resilient annular ring is secured in the annular groove by vacuum as well as by its resiliency.
 23. A nailing machine as defined in claim 8 wherein said valve sleeve has an annular groove with a vent passage extending from the bottom of the groove, said downwardly facing annular valve ring is resilient and has annular ridges on the sides thereof, said resilient annular valve ring is forced into said annular groove with the air behind said ring being vented through the vent passage, and a plug is inserted in the vent passage to close the same whereby the resilient annular ring is secured in the annular groove by vacuum as well as by its resiliency.
 24. A nailing machine as defined in claim 8 wherein said cylinder member is a two-part telescopically arranged member, the inner part includes the cylinder for the upper small diameter piston of the differential piston unit and carries the sealing means for the piston rod of the differential piston unit, the outer part slidably carries the valve sleeve, and the inner part and the outer part have mating longitudinal grooves forming the passageways for venting to atmosphere the upwardly facing annular valve seat of the cylinder member.
 25. A nailing machine as defined in claim 24 wherein said inner part and outer part of said cylinder member have registered holes forming the passageways for supplying air under pressure from the hollow housing to the cylinder below the upper small diameter of the differential piston unit.
 26. A nailing machine as defined in claim 1 wherein said cylinder sleeve, cylinder member and valve sleeve are molded from a suitable rigid synthetic plastic material.
 27. A nailing machine as defined in claim 8 wherein said cylinder sleeve, cylinder member and valve sleeve are molded from a suitable rigid synthetic plastic material.
 28. A nailing machine as defined in claim 24 wherein the inner and outer parts of the cylinder member are molded from a suitable synthetic plastic material.
 29. A nailing machine as defined in claim 2 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.
 30. A nailing machine as defined in claim 4 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the piston flange on said cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.
 31. A nailing machine as defined in claim 8 wherein said means including said control valve means includes a valve housing having first and second bores reciprocatingly receiving said first and second valves, respectively, a passage connecting the first valve to a source of air under pressure, a passage connecting the first valve to the piston flange on said cylinder sleeve, a passage connecting the first valve to the second valve, and a passage connecting the second valve to atmosphere.
 32. A pneumatically operated nailing machine including, a housing, a reciprocatable blade for driving nails when advanced, a reciprocatable air-operated piston unit in the housing connected to the blade for retracting and advancing the blade as the piston unit is raised and lowered, and means including control valve means for controlling the raising and lowering of the piston unit, the improvement wherein said means including said control valve means comprises a valve housing in the nailing machine housing having first and second bores, a first valve in the first bore having a normal position and movable to a second position when the nailing machine is placed against an object to be nailed, a second valve in the second bore having a normal position and movable to a second position when a control trigger is manually depressed, said valve housing having a first passage connecting the first valve to a source of air under pressure, a second passage connecting the first valve to the air-operated piston unit, a third passage connecting the first valve to the second valve, and a fourth passage connecting the second valve to atmosphere, the arrangement being such that the air-operated piston unit is moved downwardly to advance the nail-driving blade only when both valves are moved to their second positions.
 33. A nailing machine as defined in claim 32 wherein said valve housing has sealing means for sealing said first and second bores therein and said first and second passages.
 34. A nailing machine as defined in claim 32 wherein said valve housing is molded from a suitable rigid synthetic plastic material.
 35. A nailing machine as defined in claim 32 wherein said first valve is molded from a suitable rigid synthetic plastic material.
 36. A nailing machine as defined in claim 32 wherein said second valve is molded from a suitable resilient synthetic rUbber or rubberlike plastic material.
 37. A pneumatically operated nailing machine including a reciprocatable blade for driving nails when advanced, a reciprocatable air-operated piston unit, and means securing the blade to the piston unit to be advanced and retracted thereby, the improvement wherein the upper end of said reciprocatable blade is T-shaped, and said means for securing the blade to the piston unit includes a two-part separable holder secured to the piston unit and encompassing the upper end of said blade, said holder having shoulders engageable by the undersides of the T-shaped portion of said blade, a backup plate within the holder is engageable by the top side of the T-shaped portion of said blade when the piston unit advances the blade for driving nails. 